(PE-3659) Added Jetty server validation to service `init` exception test

This commit adds an assertion to a test that no Jetty server instance was
attached to the service context when a dependent service throws an
exception during its `init` function.

The commit also adjusts the test description to validate what it is
actually doing around the validation of the Jetty server instance.
(PE-3140) Wrap webserver start in shutdown-on-error

This commit wraps the `start-webserver` call during the `start` phase of
the webserver-jetty9 service in a `shutdown-on-error` call.  This allows
the Jetty server instance to be persisted to the service context and,
therefore, have a `stop` call for the service stop the Jetty server
instance.  Stopping of the Jetty server instance is necessary in order
for the JVM process in which the server was started to gracefully exit.